The telecoms watchdog said it could fine the operator if it fails to meet the new targets.

The price controls enforced by Ofcom will apply to the most popular broadband line used by rivals, which has a download speed of 40 megabytes per second and an upload speed of 10 megabytes per second.

However, Openreach will maintain full control over the prices for lines with an even faster speed in the hope that it will spur telecoms firms towards installing their own superfast lines to rival BT.

But Openreach questioned whether the price controls would lead to fresh investment in superfast broadband.

A spokesman for Openreach said: “Ofcom have proposed a number of ways to address fibre pricing and service so we will be reviewing these in detail, but on first viewing they don't appear to incentivise more investment in 'full fibre' networks.

"The UK needs a regulatory framework that encourages investment and rewards risk. Building digital infrastructure is very expensive with long payback periods and we won't recover our more than £3 billion investment in fibre until after this charge control period.